Apparatus for coating strip



Feb. 23, 1954 DAVE; Re. 23,787

APPARATUS FOR COATING STRIP MATERIAL Original Filed May 21, 1949 2 SheetsSheet 1 f'mfbl Herbs)?! .L-Uaw's gi /W Feb. 23, 1954 DAVls APPARATUS FOR COATING STRIP MATERIAL 2 Sheets-Sheet 2 Original Filed May 21, 1949 0 m 21 2 #411... X w w w, fix u 5 3W0 T. 2 am a x m 4|\ k .H mm m H E E named at. as, 1954 APPARATUS FOR COATING MATERIAL Herbert L. Davis. WalmhMalua-lmrto'lhe B. F. Goodrich Company, New York. N. Y., a

corporation of New York 4 No. 2,588,967, dated March 11, 1853. Serial No. 94,638, May 21, 1949. Application for reissue March 9, 1958, Serial No. 341,888

18 Claims. (Ol- 118-5) Matter enclosed inheavy brackets I: II appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to a method and apparatus for applying a coating of plastic or adhesive material to textile fabrics or other flexible backing material, and has particular reference to a method and apparatus for applying a coating of plastic material to one or both sides of the fabric stringers of slide fasteners.

It is an object of my invention to provide a method and apparatus for applying a coating of a plastic material to one or both sides of textile fabric.

It is also an object of my invention to provide a method and apparatus for applying a coating of plastic material of uniform and predetermined thickness to textile fabric.

A further object of my invention is to provide a method and apparatus for coating a predetermined zone of a fabric or other flexible base with a plastic material.

Another object of my invention is to provide an apparatus capable of continuously applying a coating of a plastic material to one or both sides of the fabric stringers of slide fasteners.

Other obiects of my invention will be apparent from the drawings and description which follow.

It is often desirable to incorporate slide fasteners into articles made of rubber or materials similar to rubber. One method of accomplishing this union is to apply a coating of adhesive composition to the portions of the fabric stringers of the slide fastener which it is desired to unite with the rubber portion of the article. and then to press the margins of the rubber article into adhesive engagement with the coated stringers.

It is desirable to use an adhesive composition free from volatile solvents as a coating material in order to eliminate the hazard of fire and the necessity for a drying period to allow the solvents to evaporate from the coating and coated article, and to decrease the necessity for frequently interrupting the coating operation to clean the apparatus. In addition, absence of a volatile solvent prevents undesired creeping or spreading of the adhesive composition beyond the boundaries of the zone or area which it is desired to treat. and makes possible better control of the thickness and distribution of the adhesive composition.

For these reasons it is desirable to use as the adhesive composition a plastic or highly viscous material free from volatile ingredients, preferably an adhesive which is vulcanizable to form a strong bond between the parts to be adhered together. Preferably a plastic mass of vulcanizable rubber material containing vulcanizing agents, accelerators, and any other conventional comp unding ingredients is employed.

To obtain a satisfactory adhesion or bondins between a coating of a viscous plastic vulcanizable rubber composition and a textile fabric or other flexible fibrous backing material the plastic coating material must be forced into the fabric or other fibrous material. Furthermore, in treating slide fasteners the adhesive must be restricted to a specified area or zone of the stringers to avoid contaminating the raceway portions of the slide fastener with gummy material which would interfere with the proper operation of the slide fastener.

The coating apparatus must be adapted to coat stringers of varying lengths, widths and thicknesses in view of the numerous sizes of slide fasteners incorporated in articles as a fastening means.

In the drawings:

Fig. l is a front elevation of an apparatus embodying my invention;

Fig. 2 is a section on line 2-4 of Fig. 1 showing the manner in which the upper roll assembly is pivotally mounted;

Fig. 3 is a section on line 3-4 of Fig. 2; and

Fig. 4 represents a slide fastener after the coating operation showing portions of the fabric stringers coated with a plastic material. v Referring to the drawings. the apparatu comprises a base plate It which forms a foundation for the lower side frames II. II which are bolted to the base plate III by bolts l2, l2 and the upper side frames [3, l3 which are connected by hinges II, it and binge pins II, I! to the lower side frame II, II. End flanges it, It, center flanges I], II and backing rolls it. it are keyed to shafts i9, 20; spacer rolls 22, 22 and coating rolls II, 23 are keyed to shafts I4, 25. The lower side frames H, H form a housing for shafts Ill. 25, and the side frames It, It form a housing for shafts Power is supplied to the apparatus through a chain and sprocket secured to shaft 25. A gear chain formed of pinion gears 26, 21, 28. 29, it and II mounted on the several shafts causes all of the shafts to rotate at the same speed, each adjacent pair of shafts being counter-rotating with respect to each other.

Positioning rods If, it slide in channels II. II in the upper side frames it, it and screw into the lower side frames I I. i 1. Compression springs it, it confined between and by flanges 35. t5 and positioning nuts 36, to apply positive downward pressure to the upper side frames 13, ll forcing the entire upper assembly downward. Flanges or steps ".11 at the lower end of the positioning rods II. 82 prevent the compression 3 springs 84, 84 from forcing the upper assembly down beyond a desired position and maintain the coating rolls 23, it in a predetermined spaced apart position.

Scraper blades 38. 38 which determine the quantity and thickness of plastic material fed onto the coating rolls 23. II are mounted on,

scraper rods 39, 39 which fit into scraper adjustment screws III, III passing through support bars ll, ll secured to the upper side frame II. II and the lower side frame II, II.

The input guide support 42 is fitted between and bolted to the lower side frames H, H and forms a support for the input guide II a portion of which fits into a rectangular milled cavity in the input guide support 42 preventing the input guide 43 from moving forward between the rolls or in a lateral direction. The output platform ll is fitted and bolted to the lower side frames II, I I and supports one end of the input guide I! when it is in working position. and it may further serve as a foundation for gears. rolls. etc. of a conveyor system (not shown) which would carry the coated slide fasteners to the next processing machine. The input guide support 2 and the output platform 44 further serve as spaced elements restraining the lower side frames H, H from lateral motion.

The metal raceways 45 of the slide fastener fit into a guideway 48 in the input guide 48 which guides the slide fastener to the coating rolls II, 23. Leaf springs l1, 41 of varying lengths are bolted to a guide-frame 48 and apply pressure to the metal raceways 4i preventing themfrom jumping out of the guideway 48. The guideframe 48 is secured to the input guide 43 and contains guide members 49. It to guide the slide fastener tab iii.

A thermostatic control I situated in a cavity is in one of the upper side frames ll. ll controls the operation of a blower fan I2 which directs cooling air through ducts against the side portions of the apparatus. Sheet metal guards 53, 53 cover the side portions of me apparatus serving not only as safety coverings over the gears, shaft ends, etc. but also forming chambers through which the cooling air flows, the air passing out of the apparatus through a space between the top of the guard and the upper side frame.

A coated slide fastener as represented in Fig. 4 consists of raceways II, a tab ill and stringers BI, 55. Portions of the stringers II. II are coated with a layer of plastic material 58. SI.

As a convenience in maintaining the apparatus in proper working order and for ease in cleaning and lubrication the positioning rods 32, 32 may be unscrewed from the lower side frames II. II and the bolts holding the sheet metal guards as, 53 may be loosened allowing the guards 53, 53 to be moved away from the apparatus permitting the entire upper assembly to be pivoted about the hinge pins ll. Ii, thereby rendering the interior portions of the apparatus readily accessible to the workmen.

Coated slide fasteners to give satisfactory service must have a strong mechanical bond between the coating and the fabric. This requires that a portion of the plastic coating be forced into the fabric material, and is accomplished in my apparatus by the pressure exerted on the coating and fabric by the coating rolls 2!, 23 which receive the main portion of their pressure from the action of the compression springs 34, 3|. To obtain the desired pressure when the machine is in operation the positioning rods 82, 82 are screwed into the lower side frames i I. H. and positioning nuts 3B, 3B are tightened until sufficient pressure is exerted by the compression springs It, 34 to maintain the desired pressure between the coating rolls 13, 23 and the slide fastener stringers Ii, ii. The compression spring assembly further serves the function of a relief system, so that, if foreign material passes between the coating rolls 2!, 28, the entire upper assembly is allowed to pivot slightly about the hinge assembly. permitting the foreign material to pass between the coating rolls 23, 23 without damaging said rolls.

The end flanges it, It and the center flanges IT, I! restrict the plastic material 84, 54 to the peripheral surfaces of the backing rolls II, II. The coating rolls 2!, I! receive the plastic material diverted from-the backing rolls II, II by' the scraper blades II, II. The backing rolls l8, it on shaft is and the coating rolls 23, 28 on shaft ll are in a fixed position relative to each other allowlm a predetermined thickness of plastic sheet to pass between them, and the backing rolls III. II on shaft it and the coating rolls 2!, II on shaft 2! are similarly arranged. Spacer roll 22 on shaft 24 prevents any lateral motion of the coating rolls II. 2! toward each other, and the spacer roll I! on shaft 25 serves the same function.

Although all of the rolls revolve at the same speed, the diameters of the backing rolls i8. i8 contacting the plastic material N. N are smaller than the diameters of the coating rolls II. 23, producing a difierential peripherisl speed between the backing rolls II, II and the coating rolls 2!, 23. This imparts a milling or churning to the plastic material, softening and warming it as it is applied to the mils; and thus eliminating preheating the plastic material. Furthermore, it is a tendency of plastic material to adhere to rolls having the slower peripheral speed which in my apparatus are the backing rolls ll. It.

The scrapers are in essence the combination of three elements, a scraper blade 38. a scraper rod Ill and an adjustment screw II. The scraper rods 3!. II have at one end a flanged or shoulder portion that fits into a recess in the adiustment screws 40, 4B, the other end being secured to the scraper blades Ill, ll. This design allows the scraper blades 38, 3| to be advanced toward or withdrawn from the surface of the rolls to permit cleaning or replacement of the blades. The scraper blades 38, it when in operating position extend into the bite of the backing rolls II, It and coating rolls :8, u, and the scrapers are adjusted, so that one edge of the scraper blades 38, ll bears against the plastic sheet adhering to the backing rolls It, II and diverts a desired portion of the plastic material toward the coating rolls II. II. A slot II. 51 in the aforementioned scraper blade edges provides a means for returning any surplus plastic material I8, It to the bank 54, it of plastic material. A second edge on the scraper blades distributes the portion of plastic material diverted from the backing rolls l8, l8 evenly over the coating rolls 2!, 2i and determines the thickness of the sheet of plastic material passed onto the coating rolls 23, 23.

The operation of the apparatus is as follows.

The positioning rods 82, 82 are screwed into the lower side frames ll, II and plastic material is added into the bite of the backing rolls II. II and the coating rolls II, II. The scraper blades ll. 88 are adjusted by the scraper adjustment screws III. III to allow a desired amount of thickness of plastic material to pass onto the coating rolls 2!, 23. The positioning nuts l. 38 are then adjusted until there is sufficient compression in springs ll, 34, so that the desired pressure is exerted on the material passing between the coating rolls 23, II.

A slide fastener is placed on the input guide 43 with the metal raceways It in the closed position and seated in the guideway 48 preferably with the tab In farthest from the rolls. As the stringers it, 55 pass between the coating rolls ll. 28. they are coated and impregnated with the plastic material.

This apparatus is capable of coating one or both sides of the stringers 55, it simultaneously. Numerous coating combinations may be eifected by placing plastic material in only those banks 54. it which feed the roll portions which bear on the portions of the stringers it. UI to which it is desired to apply a coating. For example, when it is desired to coat only the upper face of stringers 55, 55, coating material is led only into the banks 54. 54 which feed into the coating portions of the upper coating roll 23. In this instance, the bottom coating roll 23 constitutes a supporting or backing member for supporting stringers'55. 55 in their passage beneath the upper coating roll 23, as shown in Fig. 1. The coating process may be continuous and any length of slide fastener may be coated as long as plastic material is maintained in the banks 54, 5|.

In addition, it will be noted that stops 81, 31. by maintaining opposed coating rolls 23, 23 in spaced apart relation facilitate the coating of numerous short lengths of stringers since the coating rolls 23. 28 may rotate continuously, even when no stringers are passing between them, without danger of stripping the coating from one roll to the other.

At high-speed operation or when a comparatively hard plastic material is fed into the machine, heat developed by friction created by the milling action may soften the plastic material more than is desired for the coating operation. The excess heat is efiectively conducted away by blowing cool air through chambers formed by the side frames of the apparatus and guards 68, 53 which are bolted to the base plate Ill and the lower side frames II, II. The operation of a blower fan 52 may be readily controlled by a thermostatically operated switch 5| located in a cavity in one of the upper side frames l3, l3. This method of cooling has been found more satisfactory than circulating water through inner cavities in the rolls, since water cooling chills the plastic material too suddenly, and it is extremely difficult to control the water flow so that the temperature of the plastic material is maintained within a desired temperature range.

Heretofore, it has been diilicult to obtain a sharp straight line of demarcation of coating material on the fabric. My invention eliminates this difflculty. since the width of the coated portion is determined by the width of the coatin rolls 23, 23.

It is obvious that minor changes in design or material may be made without departing from the scope and spirit of the invention as defined in the appended claims.

I claim:

1. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article andapply a coating thereto. means pressing said rolls toward each other. a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, and scraper means in the nip between each said coating roll.and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll.

2. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other. a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll. said backing roll being adapted to carry coating material on its face, and scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll.

3. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingiy pressing said rolls toward each other. a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, and air cooling means for removing the heat developed in said apparatus during the operation thereof.

4. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotatlng coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other. a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face. scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, air cooling means for removing the heat developed in said apparatus during the operation thereof, and means sensitive to temperature variations in said apparatus for controlling said cooling means.

5. Apparatus for coating the stringers of a slide fastener comprising a plurality of opposed counter-rotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other. a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, and guide means to receive the teeth of a slide fastener and guide it to the coating rolls.

6. Apparatus for coating an elongated flexible article comprising a plurality of counter-rotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other, a backing roll opposed to each of said coating rolls and revolving at a lower peripheral speed than said coating roll. said backing roll being adapted to carry coating material on its face, and scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, said scraper means including means for returning to said backing rolls any surplus coating material scraped from said backing rolls.

7. Apparatus for coating an elongated flexible article comprising a pair of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, at least one of said rolls being mounted for pivotal movement to and from an operating position in which the peripheral surfaces of said rolls are closely adjacent each other, a counter-rotating backing roll opposed to each said coating roll and mounted for pivotal movement therewith, said backing roll being adapted to carry coating material on its face, means for yieldingly urging said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said coating rolls, and scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll.

8. Apparatus for coating an elongated flexible article comprising a pair of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, at least one of said rolls being mounted for pivotal movement to and from an operating position in which the peripheral surfaces of said rolls are closely adjacent each other, a counter-rotating backing roll opposed to each said coating roll and mounted for pivotal movement therewith, means for yieldingly urging said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said coating rolls, air cooling means for removing the heat developed in said apparatus during the operation thereof, and means sensitive to temperature variations in said apparatus for controlling said cooling means.

9. Apparatus for coating an elongated flexible article comprising a pair of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, at least one of said rolls being mounted for pivotal movement to and from an operating position in which the peripheral surfaces of said rolls are closely adjacent each other, a counterrotating backing roll opposed to each said coating roll and mounted for pivotal movement therewith, said backing roll being adapted to carry coating material on its face, means for yieidingiy urging said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said coating rolls, and scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, said scraper 8 means including means adapted to return to said backing rolls any surplus coating material scraped from said backing rolls.

10. Apparatus for coating an elongated flexible article comprising a first from including a coating roll and a backing roll adapted to carry coating material on its face opp sed to said coating roll, said rolls being rotatably mounted therein, a second frame including a coating roll and a backing roll adapted to carry coating material on its face opposed to said coating roll, said rolls being rotatably mounted therein, said frames being pivotally secured together about an axis remote from said rolls for movement to and from an operating position in which the coating rolls of said frames have their peripheral surfaces closely adjacent each other, means yieldingly urging said frames including said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said opposed coating rolls, means for rotating said coating rolls and said backing rolls in opposite senses to advance said article between said coating rolls and apply a coating thereto, and scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing rolls to the adjacent face of said coating roll.

ll. Apparatus for coating an elongated flexible article comprising a first frame including a coating roll and a backing roll opposed to said coating roll, said rolls being rotatably mounted therein, a second frame including a coating roll and a backing roll opposed to said coating roll, said rolls being rotatably mounted therein, said frames being pivotally secured together about an axis remote from said rolls for movement to and from an operating position in which the coating rolls of said frames have their peripheral surfaces closely adjacent each other, means yieldingly urging said frames including said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said opposed coating rolls, means for rotating said coating rolls and said backing rolls in opposite senses to advance ing material on its face opposed to said coating roll, said rolls being rotatably mounted therein, a second frame including a coating roll and a backing roll adapted to carry coating material on its face opposed to said coating roll, said rolls being rotatably mounted therein, said frames being pivotally secured together about an axis remote from said rolls for movement to and from anoperatingpositionln whlchthe coating rolls of said frames have their peripheral surfaces closely adjacent each other, means yielding urging said frames including said coating rolls toward each other, stop means for positively maintaining a predetermined interval between the peripheral surfaces of said opposed coating rolls, means for rotating said coating rolls and said baclnng rolls in opposite senses to advance said article between said coating roll and apply a coating thereto, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, and means on said scraper devices adapted to return to said backing rolls any surplus coating material scraped from said backing rolls.

13. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, means pressing said rolls toward each other, a backing roll opposed to each of said coating rolls, said backing roll being adapted to carry coating material on its face, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, and at least one air duct disposed over the ends of said coating rolls and said backing rolls adapted to convey cooling air against said ends of said coating rolls and said backing rolls.

14. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other, a backing roll opposed to each or said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, at least one air duct disposed over the ends of said coating rolls and said backing rolls adapted to convey cooling air against said ends of said coating rolls and said backing rolls, and means for causing cooling air to flow through each oi said air ducts.

15. Apparatus for coating an elongated flexible article comprising a plurality of opposed counterrotating coating rolls adapted to advance said article and apply a coating thereto, means yieldingly pressing said rolls toward each other, a backing roll opposed to each 01' said coating rolls and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, scraper means in the nip between each said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, at least one air duct disposed over the ends said coating rolls and said backing rolls adapted to convey cooling air against said ends of said coating rolls and said backing rolls, means for causing cooling air to flow through each of said air ducts, and means sensitive to temperature variations in said apparatus for controlling the flow of said cooling air.

16. Apparatus for coating a. flexible article comprising a coating roll adapted to advance said article and apply a coating thereto, a backing roll opposed to said coating roll and revolving at a lower peripheral speed than said coating roll, said caching roll being adapted to carry coating material on its face, scraper means in the nip between said coating roll and backing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the advanced jace of said coating roll, and supporting means [or supporting said article in its advanced past said coating roll.

17. Apparatus for coating 0. flexible article comprising a coating roll adapted to advance said article and apply a coating thereto, a backing roll opposed to said coating roll and revolving at a. lower peripheral speed than said coating roll, said bucking roll being adapted to carry coating material on its face, scraper means in the nip between said coating roll and baclcing roll in the delivery region thereof adapted to scrape at least a portion of said coating material from said backing roll to the adjacent face of said coating roll, and supporting means for supporting said article in its advance past said coating roll, said supporting means being movable with said article as it is advanced past said coating roll.

18. Apparatus for coating a flexible article comprising a coating roll adapted to advance said article and apply a. coating thereto, a backing roll opposed to said coating roll and revolving at a lower peripheral speed than said coating roll, said backing roll being adapted to carry coating material on its face, scraper means in the nip between said coating roll and backing roll in the delivery region thereof adapted to scrape at least a. portion of said coating material from said backing roll to the adjacent face of said coating roll, supporting means for supporting said article in its advance past said coating roll, said supporting means including a revolving supporting roll opposed to said coating roll and revolving at the some speed as and in a direction counter to said coating roll, and means pressing said coating roll toward said supporting roll.

HERBERT L. DAVIS.

References Cited in the flle of this patent or the original patent UNITED STATES PATENTS Number Name Date 437,435 Howe Sept. 30, 1890 986,062 Illingworth Mar. 7, 1911 1,404,589 Dixon Jan. 24, 1922 1,654,214 Evans Dec. 2'1, 1927 1,783,263 Schnuck Dec. 2, 1930 1,822,014 Cosgrove Sept. 8, 1931 2,133,933 Daley Oct. 18, 1938 2,198,066 Staude Apr. 23, 1940 2,287,905 Richmond et al. June 30, 1942 Certificate of Correction Reissue No. 23,787 February 23, 1954 Herbert L. Davis It is hereby certified that error appears in the tinted specification of the above numbered patent requiring correction as fol ows:

Column 10, line 11, for advanced read adjacent; line 13, for advamrmf read advance;

and that the said Letters Patent should be read as corrected above, so that the same may vonform to the record of the ease in the Patent Office.

Signed and sealed this 4th day of May, A. D. 1954.

ARTHUR W. CROCKER,

Assistant Commissioner of Patents. 

